aaronbeekay

Actually, you might have dodged a bullet by "accidentally" buying the red bulbs instead of the white ones. "White" LEDs don't emit the same wide-spectrum white that an incandescent does- they're actually a mix of a blue and a yellow that our eye sees as white. Your red taillight will happily filter out almost all of that blue and yellow, and the bulb would have looked very dim. When you buy taillight or turn-signal LED bulbs, you need to match the color of the LED to the color of the lens for it to shine through.

Yep- that's funny, I was actually just about to ask somebody about that. My bike, with the five holes, is much louder than my friend's, with the single hole. Interesting to know.

If you can't fix the clutch being hard to pull, seems like it would be much cheaper and easier to just replace the clutch lever with a longer one- you'd get more mechanical advantage that way.

I have no idea what they're for, but my '78 XS400E has them; my buddy's '82 XS400 Seca doesn't. So they're probably stock.

Sometimes if you're having trouble getting your carbs back into the carb boots, you might try loosening the clamps on the boots. Even if they seem free, the boots need to stretch to accommodate the carbs- the clamps might be inhibiting that. /has spent 15 minutes pushing on a carb before he figured this out

Just wanted to drop into this thread and say that even though I'm a rank beginner in all this stuff, it's been great watching this thread as you progressed through all these seemingly-impossible problems. I grinned like crazy when I saw your "success" post-- it really is possible! Anyway, good to hear you got that all tied up- great work on your part.

Good news- I found a problem! Tonight I checked the points and the timing, as per the service manual. The points gap is right on, right at spec (0.014-0.015 for both), so I went on to adjust the timing... but I just couldn't get the left point to test as open. Even when I could see the gap between the points, nothing I could do would make my multimeter stop beeping, except for turning the engine a bit farther... but I couldn't see how that was changing anything-- ...until I realized that the continuity broke when the right point opened! I disconnected the points from the rest of the electrical system, and sure enough, somewhere north of the points, the left and right wires are shorted together. So every time either one of them closes, both plugs fire. My guess is that I didn't notice this issue because I was only running on one cylinder- so the plug firing too often wasn't so much of an issue. But now that I have it running properly, that accounts for the backfiring and the misfiring and the rough idle, right? (Please say yes.) So tomorrow I'll dive back in and start tearing the electrical system apart. It needed a lot of work anyway... might as well get a problem fixed along with it. As a plus, doing the points and the timing was nowhere near as daunting a task as I had imagined. And, I drained the oil and realized that it was half-gas from all the overflow that was happening before I had fixed the floats- better get that fixed too. I'm well on the way to riding again!

Yes, the airboxes are in place, and yes, it's running on both cylinders.

Here's the high-quality version of the video I posted earlier:

Is that different, or more dangerous, than backfiring through the exhaust? I bet they're not. I guess that's what I'll do next- I've been avoiding them.

Oh, also- I know my carb holders are cracked on the outside, and it looks like the consensus around here is that they'll need to be replaced. My local shop is quoting me $65 for a pair- is that reasonable? I found some on this page on MikesXS (part 48-7479)- would those work? Sorry about all the questions- thanks so much for any help.

Well, HoughMade, I have no idea how you intuited my problem so well, but you did. I came back to it last night and took the mixture screws out to 4 turns, and I managed to get it to start (albeit with some difficulty). It was idling OK, so I started to balance the carbs, which went well. It smelled like it was running rich, though, and when I took the plugs out they were dark with soot, so I assumed that 4 turns was a bit much and took it down to 3.5. I had to rebalance them, and when I tried edging the pilot screws a little bit leaner, the bike started to do the "runaway RPM" thing again. When I bring it back to 4 turns, it will still idle OK most of the time, but the left pipe still smokes a bit, it seems rough to me, and now there's a sort of snapping noise coming from the exhaust. What made you suspect that making the mix richer would solve the runaway RPM issue? When I roll on the throttle, sometimes it will "stick" at whatever speed I had left it (i.e., if I rev up to 4k RPMs and then let the throttle back to idle, the engine will stay at 4K for a while). I know that my throttle cable isn't sticking - is this the same issue as the runaway RPMs? I took a short video of the bike idling when I got it to idle. I had to upload it from my phone, so it's not the best quality - I'll try and replace it with a better version tonight. You can hear the snapping noise near the end of the video.

Even with the engine jumping up to very high RPMs symptom? If you're right, I'll be very very relieved- I'll try it tomorrow.

The idle screws are currently about 1-1.5 turns out. I had them set at 2.5-3 turns out, but the bike was backfiring frequently- this is before I realized I might have a manifold leak, though, so I may have to adjust again.

Okay. Progress. I finally got the bike started that same night- I thought maybe my makeshift fuel-IV (a fuel tube attached to a Erlenmeyer filter flask) wasn't actually getting enough fuel to the engine, so I put the gas tank back on. I thought that was what solved the problem until I came back later that night and measured the battery. Turns out, the battery charger I've been using to trickle charge the battery isn't putting out any power at all... it's just "trickle-draining" the battery. *headdesk* So I jumped the bike with my friend's battery, and it fired right up. Success! I'm running on both cylinders! Unfortunately, it's running very, very poorly. It was backfiring frequently on one of the cylinders, and still smoking out of the left exhaust for a while. I tried to adjust the pilot mixture screws, but when I looked inside the carbs, it looked like the tip of one of the needles (the needles that are moved by the pilot mix screws, not the main jet needle) may have been damaged or broken. Is there any replacement for those needles? Also, I can start the bike, but often after 5-10 seconds of a high idle, the engine will start to rev up to 4-5k rpm, and hold there or continue climbing. I suspect I have a leak in the rubber manifold boots between the carbs and the engine- specifically, the left boot. I have a homemade carb balancer- one of the "long-tubing-with-ATF-inside" deals- and when I attached it to both vacuum nipples, the ATF moved up on the right side and down on the left side and kept going until I hit the kill switch. It seems to me that that's a symptom of a manifold leak, yes? I'll be back at it today- posting here is a good way to think about what I'm doing, which I'm not always so good at.